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Updated: May 29, 2026

Direct Imaging of Laser-driven Ultrafast Molecular Rotation
Published on: February 4, 2017
Vibrational excitations in molecular layers probed by ballistic electron microscopy
Rasanayagam Sivasayan Kajen1, Natarajan Chandrasekhar, Xinliang Feng
1Institute of Materials Research and Engineering, 3 Research Link, 117602, Singapore.
Abstract:
We demonstrate the information on molecular vibrational modes via the second derivative (d(2)I(B)/dV(2)) of the ballistic electron emission spectroscopy (BEES) current. The proposed method does not create huge fields as in the case of conventional derivative spectroscopy and maintains a zero bias across the device. BEES studies carried out on three different types of large polycyclic aromatic hydrocarbon (PAH) molecular layers show that the d(2)I(B)/dV(2) spectra consist of uniformly spaced peaks corresponding to vibronic excitations. The peak spacing is found to be identical for molecules within the same PAH family though the BEES onset voltage varies for different molecules. In addition, injection into a particular orbital appears to correspond to a specific vibrational mode as the manifestation of the symmetry principle.
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